1. Field of the Invention
The present invention relates to an image display apparatus having a function to correct trapezoidal distortion caused when a screen image is projected on a screen from an angle, and an information processing apparatus having the image display apparatus.
2. Description of Related Art
An image display apparatus that projects a screen image on a screen has no problem when the screen image is projected on the screen straight from a side of the apparatus. In a case where the screen image is projected on the screen from an angle, however, trapezoidal distortion occurs, in which a rectangular output screen image is distorted into a trapezoidal shape. Then, trapezoidal distortion correction (Keystone correction) is performed to convert the rectangular output screen image into a trapezoidal shape in the reverse direction of the distorted trapezoidal shape of the screen image projected on the screen. Thus, a non-distorted rectangular screen image can be displayed on the screen.
Such trapezoidal distortion correction may be configured such that a user manually makes an adjustment while viewing the screen image on the screen. Because the work of adjustment is cumbersome, a technology is known that automatically corrects trapezoidal distortion, thus eliminating manual adjustment by a user, as described in Japanese Patent Laid-open Publication Nos. H9-270979 and 2006-14233, for example. When an image display apparatus itself is installed in a tilted state, such a technology detects with a sensor an installation angle of the image display apparatus and corrects trapezoidal distortion in accordance with the installation angle.
In the conventional technology, the image display apparatus itself is installed in a tilted state. However, a projection unit of an image display apparatus may be rotatably provided in a main body so as to substantially change a projection angle. Then, a screen image can be projected on a ceiling as a screen in addition to a wall as a screen, thus enhancing usability.
Depending on a positional relationship between a user looking up to the ceiling from below and the screen image, however, the screen image appears upside down. In this case, a circumstance arises where a user needs to move or rotate the image display apparatus in order to improve viewability, and thus usability for the user is reduced.